Hearty Black Bean Chowder - Crock Pot

1 (15 ounce) can black beans , do not rinse, drain

1 (15 ounce) can diced tomatoes

1 cup frozen corn

1 (14 ounce) can fat-free refried beans (the hot ones if you like spicy)

1 cup fat free chicken broth (or vegetable broth for vegetarian's)

3 tablespoons taco seasoning

1/2-1 teaspoon cayenne pepper

1/4 cup fresh cilantro , chopped

6 tablespoons nonfat sour cream